Barrel engines have a unique advantage over crankshaft engines in that they are more compact. This is mainly because barrel engines unlike crankshaft engines comprise pistons that work in parallel to an output shaft as opposed to perpendicular. However, an energy translation mechanism such as a wobble plate, swash plate, cam, or other means is required to translate the linear motion of the pistons into rotary motion about the output shaft. These energy translating mechanisms translate the upstroke and downstroke action of a piston into rotary moment about an output shaft by placing a torque onto the output shaft.
Currently, barrel engines, as well as crankshaft engines, have reduced efficiency because piston force is dissipated in various forms such as high sliding friction caused by the torque forcing the piston into contact with the inner walls of the combustion chamber. In addition there is a minor amount of friction in the barrel engine due to the translation of the linear motion of the pistons into rotary motion of the output shaft creates a lemniscate motion. This motion is translated along the length of the piston causing the piston to act against the inner wall of the cylinder liner which in turn reduces the force of the power stroke. Accordingly, such an engine may include devices to increase engine power density, such as an air control valve. Air control valves collect compressed gas and direct the compressed gas to a combustion chamber, thereby creating more force as the fuel is introduced into the chamber and ignited. Such devices are currently separate from the barrel engine and thus the desirable compact feature of the barrel engine is diminished. Furthermore, current air control valves operate off an auxiliary output shaft thus further decreasing engine efficiency as energy is transferred from the primary output shaft to the auxiliary output shaft.
Barrel engines are also susceptible to wear, particularly at the point where the piston acts on the energy translation mechanism because of the lemniscate motion. The use of a sliding ball socket joint is currently used to mitigate wear on the energy translating mechanism. However such joint assemblies have limited the degree of movement of the energy translation mechanism about the output shaft to approximately 20 degrees, thus limiting engine stroke length. Another disadvantage of current barrel engines is that the fuel injection is located on the side of the cylinder, thus unlike crankshaft engines where the fuel is injected into the length of the cylinder, fuel in a barrel engine is injected into the side making combustion control more difficult.
In general the efficiency and power output of an engine is increased by controlling the supercharging of the engine (meaning the addition of compressed air into the combustion chamber), injecting fuel at a degree to achieve optimal combustion control, and enabling longer engine strokes relative to bore diameter. Accordingly, it is desirable to have an engine equipped with supercharging capabilities, optimal fuel injection, and long engine strokes relative to bore diameter.